JPH01198277A - Semi-conductor power converter - Google Patents

Abstract

PURPOSE:To reduce the size and to improve the efficiency, by connecting a gapless arrester to AC side of a bridge circuit and absorbing only commutation energy when forcible commutation is made. CONSTITUTION:A semi-conductor power converter comprises an AC power source 1, a single-phase bridge circuit 3, GTO thyristors 4-7, snubber circuits 8-11 and a smoothing reactor 12, and drives a DC load, i.e. a motor. A gapless arrester 18 operable with a voltage higher than the peak voltage of the AC power source 1 is connected, in place of a commutation energy absorbing circuit, between AC side terminals of the bridge circuit 3. Since the voltage of the gapless arrester 18 connected to AC side of the bridge circuit 3 does not reach to the limit voltage thereof and no current flows through the arrester 18, power is not consumed through the arrester 18. When control is made such that the commutation margin angle is negative, peak voltage is produced to cause current flow through the arrester 18 thus absorbing commutation energy.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a semiconductor power conversion device that uses a self-extinguishing semiconductor switching element such as a GT○ thyristor as a power conversion element and can regenerate power to an AC power source. Regarding equipment.

(Prior Art) Conventionally, as this type of semiconductor power converter device, a thyristor without a self-extinguishing function and a GTO having a self-extinguishing function have been used.
2. Description of the Related Art Semiconductor power conversion devices are known that include a bridge circuit made of semiconductor switching elements such as thyristors.

Here, in a semiconductor power conversion device using a semiconductor switching element that does not have a self-extinguishing function, the firing angle is controlled to be almost zero during forward conversion, so the DC voltage decreases by the commutation type angle. , and the DC average voltage also decreases. Furthermore, the power factor also decreases because the phase of the current on the alternating current side is delayed by the inductance on the alternating current power supply side by approximately the angle of the commutation type.

Furthermore, during inverse conversion, the control lead angle must be greater than or equal to the commutation type lead angle in order to ensure commutation margin angle, so the average voltage on the DC side decreases and the AC phase advances significantly. , the power factor also decreases more than during forward conversion.

On the other hand, in semiconductor power converters using self-extinguishing semiconductor switching elements such as GTO thyristors, each GTO thyristor is turned on or off when the polarity of the AC power supply voltage is reversed, so the commutation type angle becomes zero. be able to. Therefore, the power factor can be set to approximately 1 during both forward conversion and reverse conversion, and the DC output voltage during forward conversion and the DC voltage during reverse conversion do not decrease, making it possible to maintain a power factor of approximately 1. The drawbacks of semiconductor power conversion devices are solved to some extent.

However, when such a self-extinguishing semiconductor switching element is used, a current equal to the load current must be forcibly cut off during commutation, so it is necessary to provide a large-capacity snubber circuit to the switching element. At the same time, it is necessary to provide an energy absorption circuit on the AC side of the bridge circuit to absorb the large amount of energy stored on the AC side immediately after commutation. Therefore, a new drawback arises in that the power conversion device becomes larger.

Therefore, in order to solve the above-mentioned drawbacks, the inventor first proposed a control method for a semiconductor power conversion device, in which the self-extinguishing type semiconductor switch element is not self-extinguished during forward conversion operation of the power conversion device, and separately excited type power conversion operation is performed. In addition, a control method was proposed in Japanese Patent Application No. 62-88364 in which the ignition is controlled so that the commutation margin angle becomes zero during the reverse conversion operation, and the semiconductor switching element is self-extinguished when the power supply voltage is reversed. did.

In order to implement this method, for example, a semiconductor power conversion device shown in FIG. 4 was devised.

That is, in the figure, 1 indicates an AC power supply, 2 indicates an inductance on the AC side, and the AC power supply 1 includes reverse blocking type GTo thyristors 4 to 7 as self-extinguishing semiconductor switching elements.
A single-phase bridge circuit 3 configured by is connected thereto. Snubber circuits 8 to 11 for protecting the thyristors from overvoltage are connected in parallel to each of the GTO thyristors 4 to 7, and a commutating energy absorption circuit 14 is connected in parallel to the AC power supply 1.

At the knee, the commutation energy absorption circuit 14 is a diode bridge 15. The input terminal of the diode bridge 15 is connected to the AC power supply 1, and the output terminal is connected to a parallel circuit of the capacitor 16 and the resistor 17.

Furthermore, a series circuit of a smoothing reactor 12 and a motor 13 as a DC load is connected to the DC side of the bridge circuit 3.

Next, the operation of this semiconductor power conversion device will be explained with reference to FIG.

First, Figure (a) shows the operating waveform during forward conversion. In the figure, V is the voltage waveform of the AC power supply 1, Ed is the waveform of the DC side terminal voltage of the bridge circuit 3, and i is the AC power supply. 1 and 12 represent the waveforms of the currents flowing through the GTO thyristors 4, 7 and 5, 6, respectively.

Initially, GTO thyristors 4 and 7 are conducting, and GTO
Assume that TO thyristors 5 and 6 are in a reverse blocking state. In this case, at time T1, the GTO thyristors 4 and 7 are not turned off by the gate signal, the on-gate signal is stopped, and the GTO thyristors 4 and 7 are not turned off by the gate signal.
The TO thyristors 5.6 are fired by applying a positive signal to their respective gates. Then, since a reverse voltage is applied between the anode and cathode of the GT○ thyristors 4 and 7, the GTO thyristor 4.
7 is extinguished and a reverse blocking state occurs.

Next, at time T2, the GTO thyristor 4.7 is turned on, and after the commutation type turn angle U has elapsed, the GTO thyristors 5 and 6 are turned off. Thereafter, the commutation is repeated in the same manner.

FIG. 5(b) is an operating waveform diagram during inverse conversion. First, when the voltage V of the AC power supply 1 is positive, the GTO thyristors 5 and 6 are in a conductive state, and the GTO thyristors 4 and 7 are in a conductive state.
is in a reverse blocking state. At this time, the current on the AC side is flowing in the direction of the dotted line shown in Figure 4, so
The DC side terminal voltage Ed of the bridge circuit 3 is negative.

Next, at the firing delay angle α, that is, at time T1, the GTO thyristors 5 and 6 are not turned off by the gate signal, the on-gate signal is stopped, and a positive signal is given to the respective gates of the GT○ thyristors 4 and 7. When ignited by
Since a reverse voltage is applied between the anode and cathode of the O thyristors 5 and 6, these GTO thyristors 5 and 6 are extinguished after commutation angle U has passed. Here, the firing delay angle α is set so that commutation of the GTO thyristors 4 to 7 ends at time T0 when the polarity of the power supply voltage V is reversed. As can be seen from the waveform of Ed, (ignition delay angle α) + (commutation type angle u) = π (rad,
), which means that the commutation margin angle is zero.

This makes it 1 time T. Therefore, no commutation energy is generated due to the cutoff of the GT○ thyristor that should be extinguished.

Thereafter, the GTO thyristors 4 and 7 and the GTO thyristors 5 and 6 repeat firing and extinguishing in the same manner.

In order to make this commutation margin angle zero, for example, a conventionally known commutation margin angle constant control method may be used.

As mentioned above, commutation is completed when the AC power supply voltage is reversed,
By adopting a control method in which the GTO thyristor is fired in advance at the firing delay angle α so as to make the commutation margin time zero, it is possible to make the commutation energy absorption circuit unnecessary.

However, even if control is performed using a constant commutation margin angle control method to make the commutation margin angle zero during inverse conversion, control delays in the commutation margin angle control system and sudden changes in the power supply voltage may cause the AC power source to At the time of voltage reversal (time T0 in FIG. 5(b)), commutation may not have been completed yet, or there may be cases where commutation has already been completed. For this reason, it is necessary to apply an off-gate signal to the GTO thyristor to be turned off at the time T0 to forcibly turn it off.

FIG. 6 is a waveform diagram for explaining the operation at this time.

Figure (a) shows the case where the commutation margin angle becomes zero as per the control command, Figure (b) shows the case where the commutation has not yet finished when the AC power supply voltage reverses, and Figure (c) shows the respective operating waveforms when commutation has already been completed. In each of these figures, υC represents the voltage across the capacitor 16, and IR represents the current flowing through the resistor 17.

Here, we will introduce 4 GTO thyristors that should be extinguished from now on.
, 7, and the GTO thyristors to be made conductive are 5 and 6. In the same figure (b), commutation is not completed at point A where the polarity of AC power supply voltage V is reversed, and these GTO thyristors are forced by the negative signal applied to the gates of GTO thyristors 4 and 7. This shows the state where the arc is extinguished.

Moreover, the reason why a peak appears in the waveform of Ed in FIG. 4B at the time of forced commutation is due to the influence of the inductance 2 on the AC side.

That is, since the GTO thyristors 4 and 7 that should be turned off forcibly cut off the current ΔId, ΔId of the current flowing on the AC side flows into the capacitor 16 via the diode bridge 15 of the commutation energy absorption circuit 14. Therefore, the voltage υC of the capacitor 16 appears in the output voltage Ed of the bridge circuit 3. Here, the time ΔTc until the capacitor voltage υC reaches its peak value Vc is ignored because the voltage value after polarity reversal of the AC power source 1 is small, and assuming that the capacitor voltage υC is also constant Vc, the following equation is obtained.

Here, L is the value of inductance 2 on the AC side.

In addition, in the case of Fig. 6 (a) and (c), since no commutation energy is generated, the voltage υC of the capacitor becomes the peak value Vp (constant value) of the AC power supply voltage V, and the resistor 17 is set according to this value. Current IR will flow.

(Problem to be Solved by the Invention) However, in this control method, the diode bridge 15. Since the commutation energy absorption circuit 14 consisting of a capacitor 16 and a resistor 17 is employed, the following problems occur.

First, during inverse conversion, the capacitor 16 is always charged to a value higher than the peak voltage value VP of the AC power source 1, so the resistor 17
Electricity is constantly generated. That is, power is generated in the resistor 17 even when the commutation energy absorption circuit 14 is substantially unnecessary during the inverse conversion operation as shown in FIGS. 6(a) and 6(c).

Furthermore, even though no commutation energy is generated during the forward conversion operation of the separately excited operation, much larger power is generated in the resistor 17 than the commutation energy generated during commutation. For this reason, commutation energy absorption circuit 14
The efficiency of the converter is poor, and there is a limit to miniaturization due to its circuit configuration, leading to an increase in the size of the commutation energy absorption circuit 14 and, in turn, to an increase in the size and lower efficiency of the power converter.

The present invention has been proposed in order to solve the above problems, and uses a small and highly efficient commutation energy absorption circuit that can absorb only the commutation energy generated when the current of a self-extinguishing semiconductor switching element is interrupted. The purpose of this invention is to provide a compact, lightweight, low-cost, and highly efficient semiconductor power conversion device.

(Means for Solving the Problems) In order to achieve the above object, the present invention prevents the generation of a high voltage higher than the peak value of the AC power supply voltage due to the AC side inductance when the self-extinguishing semiconductor switching element interrupts the current. In order to absorb commutation energy with an arrester that operates at a high voltage higher than this peak value, a gapless arrester was connected to the alternating current side of a bridge circuit consisting of a self-extinguishing semiconductor switching element. Features.

Note that as the gapless arrester, it is desirable to use a nonlinear resistance element or a zinc oxide type arrester.

(Function) According to the present invention, during forward conversion, the voltage of the gapless arrester connected to the AC side of the bridge circuit does not reach its limit voltage, and no current flows through the arrester, so there is no power consumption in the arrester.

Also, during inverse conversion, if control is performed so that the commutation margin angle is zero as per the control command, that is, the commutation type angle becomes equal to the control lead angle, the self-extinguishing type that should be arc-extinguished. The semiconductor switch element is not forcibly extinguished, and only the AC power supply voltage is applied to the gapless arrester, but this arrester does not operate and no current flows through the arrester.

Furthermore, if control is performed so that the commutation margin angle is positive, that is, the commutation type angle is smaller than the control advance angle, the self-extinguishing semiconductor switching element that should be arc-extinguished has already been extinguished. At this time, only the AC power supply voltage is applied to the gapless arrester, and no current flows through the arrester.

Then, when control is performed so that the commutation margin angle is negative, that is, the commutation type angle becomes larger than the control lead angle, the change in the current flowing on the AC side is transferred between the AC side terminals of the bridge circuit. A peak voltage is generated due to the influence of the AC side inductance. This voltage is applied between the terminals of the gapless arrester for a minute time, current flows through the arrester, and commutation energy is absorbed.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration of the semiconductor power conversion device according to this embodiment, and each component 1 to 13 in the figure is the fourth
The components 1 to 13 in the figure are the same, that is, 1 is an AC power supply, 2 is an inductance on the AC side,
3 is a single-phase bridge circuit, 4 to 7 are GTO thyristors that are self-extinguishing semiconductor switching elements, 8 to 11 are snubber circuits to protect each thyristor from overvoltage, 12 is a smoothing reactor, and 13 is a DC load. motors are shown respectively.

In the figure, 18 is a gapless arrester that operates at a voltage higher than the peak value of the voltage of the AC power supply 1. This gapless arrester 18 is connected between the AC side terminals of the bridge circuit 3 in place of the commutation energy absorption circuit 14 shown in FIG. 4, and uses, for example, a zinc oxide type arrester.

The operation of this embodiment will be explained below.

First, during forward conversion, the effect is almost the same as that previously explained in FIG. The voltage υarr is always smaller than the peak value Vp of the power supply voltage, and the gearless arrester 18 never operates. Therefore, the gapless arrester 18 has a current i
Arr does not flow, and power is not generated by resistance as in the conventional case.

Next, the operation during inverse conversion will be explained in detail.

First, when the voltage V of the AC power supply 1 is positive, the GTO thyristors 5 and 6 are placed in a conductive state, and the GTO thyristors 4 and 7 are placed in a reverse blocking state. At this time, since the current on the alternating current side is flowing in the direction of the dotted line in FIG. 1 as 12, the terminal voltage Ed on the direct current side of the bridge circuit 3 is negative.

Next, the GTO thyristors 5 and 6 are not turned off by the gate signal, but the on-gate signal is stopped, and the GT○ thyristors 4 and 7 are fired by giving a positive signal to each gate with a certain firing delay angle. GTO thyristor 5,
Since a reverse voltage is applied between the anode and cathode of GTO thyristors 5 and 6, these GTO thyristors 5 and 6 are extinguished after passing the commutation type turning angle. Here, the firing delay angle is set so that the commutation of the GTO thyristors 4 to 7 ends at the time when the polarity of the power supply voltage V is reversed.

Figures 2 (a) to (c) are the same as Figure 6 (a) described above, respectively.
~ (c), and Fig. 2 (a) shows when the commutation margin angle becomes zero according to the control command, and Fig. 2 (b) shows that commutation has not yet finished when the AC power supply voltage V is reversed. If you haven't,
FIG. 6(c) shows the operating waveform when commutation has already been completed. In each of these figures, as in FIG. 6, V represents the voltage of the AC power supply 1, Ed represents the DC side terminal voltage of the bridge circuit 3, and 11 and 12 represent the current flowing through the AC power supply 1 in the positive or negative direction. In addition, υarr represents the voltage applied to the gapless arrester 18, and i_arr represents the current flowing through the gapless arrester 18.

During reverse conversion, the commutation margin angle is zero according to the control command,
That is, when control is performed so that the commutation type angle U becomes equal to the control advance angle γ, the GTO thyristors 5 and 6 are not forcibly extinguished, and only the AC power supply voltage V is applied to the gapless arrester 18. become. At this time, the gapless arrester 18 does not operate, and the current i arr does not flow (see FIG. 2(a)).

Next, when control is performed so that the commutation margin angle is negative, that is, the commutation type angle U is larger than the control advance angle γ,
A peak voltage V arr is generated between the AC side terminals of the bridge circuit 3 due to the change ΔId of the current flowing on the AC side and the influence of the inductance 2 . This voltage Varr will be applied between the terminals of the gapless arrester 18 for a time ΔTarr expressed by the following equation.

However, when the GTO thyristors 5 and 6 forcibly cut off the current, the AC side terminal voltage of the bridge circuit 3 is limited to the arrester limit voltage V arr, and the current 1 flowing through the power supply 1 is
1 (=ΔId) via the gapless arrester 18 (
iarr==ΔId) flows to the GTO thyristor 6 (see FIG. 2(b)).

Furthermore, if the commutation margin angle is negative, that is, if control is performed so that the commutation type angle U is smaller than the control advance angle γ, the GTO thyristors 5 and 6 are already extinguished and the commutation is completed. Therefore, only the AC power supply voltage ■ is applied to the gapless arrester 18, and the gapless arrester 18 does not operate and the current iarr does not flow (the second (See figure (Q)).

In other words, the GTO thyristor is not forcibly extinguished as shown in Figure 2 (
In the cases of a) and (C), no current flows through the gapless arrester 18, and the current flows only in the case of forced extinguishment in the same figure (b).

In this embodiment, a zinc oxide type arrester utilizing the voltage-current nonlinearity of a zinc oxide element is used as the gapless arrester 18, and this arrester has excellent voltage limiting characteristics. Figure 3 shows an example of its characteristics. Below the peak value Vp of the AC power supply voltage, the arrester receives a current i ar
It is clear that if r does not flow and the GTO thyristor forcibly interrupts the current, the arrester voltage υarr is limited by the limiting voltage Varr.

Here, the gapless arrester 18 is of course not limited to the zinc oxide type arrester described above, and may use other nonlinear resistance elements as long as they have similar characteristics.

In the example shown in FIG. 2(b), the energy Qarr generated in the arrester is Qarr = L'ΔId" (Ju1
becomes.

Although the above embodiment describes the case where the load of the semiconductor power conversion device is the DC motor 3, the present invention is also applicable to the case where the load is an inverter that drives an AC motor. Furthermore, if the inverter is a voltage type inverter, a circuit switch for switching the polarity of current may be provided between the power converter and the inverter.

Further, although the above embodiments show the case where the AC power source is a single phase, it goes without saying that the present invention can be similarly applied to a multiphase AC power source such as a three-phase AC power source.

(Effects of the Invention) As described above, according to the present invention, in a semiconductor power conversion device using a self-arc-extinguishing semiconductor switching element, a gapless arrester is connected to the AC side of the bridge circuit, and the self-arc-extinguishing semiconductor switching element Since the arrester absorbs only the commutation energy generated when commutation is forcibly performed by interrupting the current, wasteful power consumption of the commutation energy absorption circuit during reverse conversion and forward conversion operations is eliminated. Therefore, it is possible to make the commutation energy absorption circuit, and thus the power conversion device, smaller and lighter, have higher efficiency, and further reduce the cost.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention,
Figure 1 is a circuit diagram showing the overall configuration, Figures 2 (a) to (c)
is an operating waveform diagram during inverse conversion in Figure 1, Figure 3 is a characteristic diagram of a zinc oxide type arrester, Figure 4 is a circuit diagram showing a conventional example, and Figures 5 (a) and (b) are respectively Operation waveform diagrams during forward conversion and inverse conversion in the figure, Fig. 6 (a) to (c)
is an operation waveform diagram during inverse conversion in FIG. 4. 1... AC power supply 3... Bridge circuit 4-7... GTO thyristor 18... Gapless arrester Patent applicant Fuji Electric Co., Ltd. agent Patent attorney Mori 1) Male 1 Figure 1 employment〃 jI3 diagram → V-TE Figure 2 j Figure 5 + a〕(b) Figure 6

Claims (1)

[Scope of Claims] A bridge circuit comprising a self-extinguishing semiconductor switching element as a power conversion element is provided, and during forward conversion, the semiconductor switching element performs a separately excited power conversion operation without self-extinguishing, and performs reverse conversion. In a semiconductor power converter device that sometimes performs ignition control so that the commutation margin angle becomes zero, and also self-extinguishes the semiconductor switch element when the voltage of the AC power supply is reversed, the AC power supply voltage is connected to the AC side of the bridge circuit. A semiconductor power conversion device characterized in that a gapless arrester that operates at a voltage higher than the peak value of is connected.